• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.15 no.2
• /
• pp.189-194
• /
• 2015

In this study, the heat radiation performance of COB LED according to the structure of thermoelectric device were compared. Thermoelectric device of the sheet copper structure and ceramic structure were used for bonding with the heating part of the COB LED. The temperature distribution in the bonding part of the thermoelectric device of COB LED was measured with a contact-type thermometer. The temperature variation of the thermoelectric device was measured by inputting the currents of 0.1A, 0.3A, 0.5A, and 0.7A. When 0.7A was applied, the temperature of the bonding part where there was a heat aggregation phenomenon of the COB LED was $59^{\circ}C$ for thermoelectric device of the sheet copper structure and $67^{\circ}C$ for the thermoelectric device of the ceramic structure. Therefore, the sheet copper thermoelectric device whose temperature was lower by $9^{\circ}C$ showed better heat radiation performance than those of the ceramic structure.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.22 no.4
• /
• pp.664-669
• /
• 2018

To observe the relationship between the oxygen vacancy and electrical characteristics of $TiO_2$ due to the $CO_2$ gases, the $TiO_2$ were deposited by the mixing gases of $Ar:O_2=20$ sccm:20 sccm and annealed with various temperatures. The bonding structure was changed with the annealing temperature from amorphous to crystal structure, and the oxygen vacancy was also changed with these bonding structures. The $CO_2$ gas reaction of $TiO_2$ films showed the variation in accordance with the bonding structure. The capacitance increased at the amorphous structure $TiO_2$, and the current also increased. However the oxygen vacancy decreased at this amorphous structure $TiO_2$. Because of the formation of oxygen vacancies is in inverse proportion to the amorphous structure. Moreover, the diffusion current in the depletion layer such as the amorphous structure showed the difference in accordance with the $CO_2$ gas flow rates.

• Journal of the Korean Society for Precision Engineering
• /
• v.27 no.8
• /
• pp.76-83
• /
• 2010

Metallic sandwich panels with pyramidal truss structures are high-stiffness and high-strength materials with low weight. In particular, bulk structures have enough space for additional multi-functionalities. In this work, in order to fabricate 3-D structures efficiently, Layered Manufacturing Method (LMM) which was composed of three steps, including crimping process, stacking process and bonding process using rapid infrared brazing, was proposed. The joining time was drastically reduced by employing infrared brazing of which heating rate and cooling rate were faster than those of conventional furnace brazing. By controlling the initial cooling rate slowly, the bonding strength was improved up to the level of strength by conventional vacuum brazing. The observation of infrared brazed specimens by optical microscope and SEM showed no defect on the joining sections. The experiments of 1-layered pyramidal structures and 2-layered pyramidal structures subject to 3-point bending were conducted to determine structural advantages of multilayered structures. From the results, the multi-layered structure has superior mechanical properties to the single-layered structure.

• Advances in materials Research
• /
• v.6 no.3
• /
• pp.245-255
• /
• 2017

High energy ball milling is employed to produce iron matrix- multiwall carbon nanotube (MWCNT) reinforced composite. The damage caused to MWCNT due to harsh ball milling condition and its influence on interfacial bonding is studied. Different amount of MWCNT is used to find the optimal percentage of MWCNT for avoidance of the formation of chemical reaction product at the matrix - reinforcement interface. Effect of process control agent is assessed by the use of different materials for the purpose. It is observed that ethanol as a process control agent (PCA) causes degradation of MWCNT reinforcements after milling for two hours whereas solid stearic acid used as process control agent, allows satisfactory conservation of MWCNT structure. It is further noted that at a high MWCNT content (~ 2wt.%), high energy ball milling leads to reaction of iron and carbon and forms iron carbide (cementite) at the iron-MWCNT interface. At low percentage of MWCNT, dissolution of carbon in iron takes place and the amount of reinforcement in iron matrix composite becomes negligibly small. However, under the present ball milling condition (ball to metal ratio~ 6:1 and 200 rpm vial speed) iron-1wt.% MWCNT composite of good interfacial bonding can retain the tubular structure of reinforcing MWCNT.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2011.08a
• /
• pp.216-216
• /
• 2011

We will investigate the bonding configurations of phenylalanine and tyrosine adsorbed on the Ge(100) surface using CLPES and DFT calculations. First, the C 1s, N 1s, and O 1s spectra obtained at 300 K revealed that both the amine and carboxyl groups of phenylalanine and tyrosine concurrently participated in adsorption on the Ge(100) surface without bond breaking using CLPES, depending on the extent of coverage. In the second place, we confirmed that the "O-H dissociated-N dative bonded structure" is the most stable structure implying kinetically favorable structure, and the "O-H dissociation bonded structure" is another stable structure manifesting thermodynamically advantageous structure using DFT calculations. This tendency turns up both phenylalanine and tyrosine, similarly. Furthermore, through the CLPES data and DFT calculation data, we discovered that the "O-H dissociated-N dative bonded structure" and the "O-H dissociation bonded structure" are preferred at 0.30 ML and 0.60 ML, respectively. Moreover, we found that the phenyl ring of phenylalanine is located in axial position to Ge(100) surface, but the phenyl ring of tyrosine is located in parallel to Ge(100) surface using DFT calculations.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.23 no.1
• /
• pp.84-91
• /
• 2013

Ultrasonic flip-chip bonding needs a precise bonding tool which delivers ultrasonic energy into chip bumps effectively to use the selected resonance mode and frequency of the horn structure. The bonding tool is excited at the resonance frequency and the input and output ports should locate at the anti-nodal points of the resonance mode. In this study, we propose new design method with topology optimization for ultrasonic bonding tools. The SIMP(solid isotropic material with penalization) method is used to formulate topology optimization and OC(optimal criteria) algorithm is adopted for the update scheme. MAC(modal assurance criterion) tracking is used for the target frequency and mode. We fabricate two prototypes of ultrasonic tools which are based on 3D optimization models after reviewing 2D and 3D topology optimization results. The prototypes are satisfied with the ultrasonic frequency and vibration amplitude as the ultrasonic bonding tools.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.23 no.6
• /
• pp.47-53
• /
• 2023

In this paper, We designed a waveguide-type feed structure that converts millimeter wave dual-polarized signals into monopulse signals and presented a manufacturing method. At millimeter-wave such as the W band, the size of the waveguide is very small, making it very difficult to manufacture complex structures. Therefore, because manufacturability is important for the waveguide-type feed structure in the millimeter-wave, electro forming and diffusion bonding were proposed and verified in this study. The designed monopulse feed structure consists of eight 180° hybrids that combine 90° hybrids and self-compensating phase shifters, and four OMTs to separate dual polarization. The designed feed structure was designed to facilitate electro forming and diffusion bonding, and the manufactured feed structure was verified through a network analyzer. It was confirmed that the two proposed production methods produce a monopulse signal well through the measured magnitude and phase of the port.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2001.05a
• /
• pp.69-74
• /
• 2001

Steel plate or fiber composite plate are mainly used in externally bonding method. Shear strengthening by externally bonding method is to confirm shear safety and to avoid brittle failure. In case of strengthening by externally bonding method, a failure of structure occurs frequently due to delamination between strengthening plate and concrete. Therefore, it is important to consider the delamination in the strengthening design. The objective of this study is to propose a modified shear strength evaluation by considering the delamination. The delamination criteria of strengthening plate is established by the ultimate strain and shear stress. And shear strength of RC beams is proposed in terms of the delamination criteria. The proposed shear strength is compared with test results and verified through the comparison.

• Journal of the Korean Institute of Telematics and Electronics D
• /
• v.34D no.2
• /
• pp.1-9
• /
• 1997

For the reduction of parasitic inductance and matching of bonding wire in the package of microwave devices, we propose multiple bonding wires buried in a dielectric material of FR-4 composite. This structure is analyzed using the method of moments (MoM) and compared with the common bondwires and ribbon interconnections. The FR-4 composite is modelled by the cole-cole model which can consider the loss and the variation of the permittivity in a frequency. At 20 GHz, the parasitic reactance is reduced by 90%, 80%, 60% compared to those of a single bonding wire in air, double bonding wires in air and ribbon interconnection in air, respectively. Also, the new bondwire shows very good matching of 60.ohm characteristic impedance and has 15dB, 10dB, 5dB improvement of the return loss and 2.5dB, 0.7dB, 0.2dB improvement of the insertion loss compared to the common interconnections. This technique can minimize the parasitic effect of bondwires in microwave device packaging.

• Proceedings of the KIEE Conference
• /
• 2008.07a
• /
• pp.470-471
• /
• 2008

SVL is installed at underground transmission system to protect cables and insulation joint-box from overvoltages caused by lightning, switching, and line-to-ground fault. Domestic underground power system adopts cross bonding type to reduce the induced voltage at sheath, but single-point bonding is required depending the system installation configuration. SVL can be easily broken by overvoltages induced at joint-box because single-point bonding has uneffective system structure to extract fault current. ANSI/IEEE recommends Parallel Ground Continuity Conductor(PGCC) to prevent SVL breakdown. In this paper, EMTP simulation is performed to analyze effects on SVL under PGCC installation when single-line-to-ground fault occurs. The result shows that PGCC and short single-point bonding distance can reduce overvoltages at SVL.